Why Does Defining the U.S. Extended Continental Shelf Matter?

Posted by Brian Van Pay
September 18, 2008
Coast Guard Cutter Healy

About the author: Brian Van Pay is a Maritime Geographer with the Bureau of Oceans and International Environmental and Scientific Affairs. He is currently on the U.S. Coast Guard Cutter Healy on the Arctic Ocean.

For this posting, I'll explain a bit why the United States, Canada, and many other coastal nations are going through the effort and expense to define their extended continental shelves. As I mentioned in the previous entry, defining a continental shelf beyond 200 nautical miles is based in international law, specifically the 617 words of Article 76 in the Convention on the Law of the Sea. In fact, about 60 coastal nations likely have a continental shelf that qualifies.

So why does defining the extended continental shelf matter? The United States, like other countries, has an inherent interest in knowing, and declaring to others, the exact extent of our sovereign rights in the ocean. Specifically, a nation has sovereign rights over the resources on and under the seabed including "sedentary" critters such as clams, crabs, and corals. While there may also be some petroleum resources (oil, gas, gas hydrates) beyond 200 nautical miles too, we'd expect to see more mineral resources, such as manganese nodules, ferromanganese crusts, and polymetallic sulfides. Defining those rights in concrete geographical terms provides the specificity and certainty necessary to protect or use those resources.

Because most of the ocean -- especially the deep ocean -- is unexplored, we are unsure what exactly is down there. But given the size of the U.S. continental shelf, the resources are probably worth many billions of dollars. In some ways, this is sort-of like the purchase of Alaska, with the exception that we are defining an area where we already have rights.

In fact, one study estimates the U.S. extended continental shelf totals at least one million square kilometers or about twice the size of California! This is not limited to the Arctic Ocean; the United States also has extended continental shelf off other areas, too, such as the East Coast, the Gulf of Mexico, and the Northern Mariana Islands and Guam. We have been working just as hard the past six years to collect and analyze data in those areas as well.

Some of the more immediate benefits are the interesting scientific discoveries. The data from the last three cruises to the Arctic revealed scours created by past glaciers scraping along the ocean bottom, and large craters thought to be formed by gas seeps emanating from the ocean floor. One of these missions even discovered a 3,000 meter tall underwater mountain, subsequently named the Healy Seamount, that had never been mapped before! These data also provide the basic information necessary to gain better scientific insights into climate change, marine ecosystems, and hazards resulting from extreme events, such as earthquakes and tsunamis.

If you want to learn more about the types of data we are collecting, the cooperative effort with Canada, and life onboard an icebreaker, then check back for my future entries on DipNote.

Editor's Note: This is the second in a series of postings by Brian Van Pay about his assignment aboard the Healy. Read his first entry or next one.



New York, USA
September 19, 2008

Siense in New York writes:

I agree that we need a better scientific knowledge of this topic as well.

Florida, USA
September 19, 2008

Susan in Florida writes:

A question -- what defines a nation's continental shelf? I mean, does a nation's rights to the land under the ocean have to do with a nation's size and length of coastlines or a nation's standing in the world? Are these obvious questions that answer themselves --because I really am not sure I know the answers. Thank you for this posting and for the photos -- very informative.


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